A. Drobshoff

Strontium and barium iodide high light yield scintillators

Europium-doped strontium and barium iodide are found to be readily growable by the Bridgman method and to produce high scintillation light yields.

104 MHz rate single-shot recording with subpicosecond resolution using temporal imaging.

We demonstrate temporal imaging for the measurement and characterization of optical arbitrary waveforms and events. The system measures single-shot 200 ps frames at a rate of 104 MHz, where each frame is time magnified by a factor of -42.4x. Impulse response tests show that the system enables 783 fs resolution when placed at the front end of a 20 GHz oscilloscope. Modulated pulse trains characterize the systems impulse response, jitter, and frame-to-frame variation.

Ce-doped single crystal and ceramic garnet for γ-ray detection

Ceramic and single crystal Lutetium Aluminum Garnet scintillators exhibit energy resolution with bialkali photomultiplier tube detection as good as 8.6% at 662 keV. Ceramic fabrication allows production of garnets that cannot easily be grown as single crystals, such as Gadolinium Aluminum Garnet and Terbium Aluminum Garnet. Measured scintillation light yields of Cerium-doped ceramic garnets indicate prospects for high energy resolution.

Barium iodide single-crystal scintillator detectors

We find that the high-Z crystal Barium Iodide is readily growable by the Bridgman growth technique and is less prone to crack compared to Lanthanum Halides. We have grown Barium Iodide crystals: undoped, doped with Ce3+, and doped with Eu2+. Radioluminescence spectra and time-resolved decay were measured. BaI2(Eu) exhibits luminescence from both Eu2+ at 420 nm (~450 ns decay), and a broad band at 550 nm (~3 μs decay) that we assign to a trapped exciton. The 550 nm luminescence decreases relative to the Eu2+ luminescence when the Barium Iodide is zone refined prior to crystal growth. We also describe the performance of BaI2(Eu) crystals in experimental scintillator detectors.

Compact fiber laser approach to generating 589 nm laser guide stars

We are developing an all-fiber laser system for generating 589 nm light for laser-guided adaptive optics. If only natural stars can be used to measure the turbulence in the Earths atmosphere, at most a few percent of the sky is accessible to adaptive optics correction. Laser guide stars are therefore crucial to the broad use of adaptive optics, because they facilitate access to a large fraction of possible locations on the sky. In particular, lasers tuned to the 589 nm resonance line of atomic sodium are able to create an artificial beacon at altitudes of 95-105 km, thus coming as close as possible to reproducing the light path of starlight. The deployment of multiconjugate adaptive optics on large aperture telescopes world-wide will require the use of three to five sodium laser guide stars in order to achieve uniform correction over the aperture with a high Strehl value. Current estimates place the minimum required laser power at 10 W per laser for a continuous wave source. In addition, the lasers need to be compact, efficient, robust and turnkey.

Thermally induced dephasing in periodically poled KTiOPO4 nonlinear crystals

Experimental data that exhibits a continuous-wave, second-harmonic intensity threshold (15 kW/cm2) that causes two-photon nonlinear absorption which leads to time-dependent photochromic damage in periodically poled KTiOPO4 is presented and verified through a thermal dephasing model.

745 fs Resolution Single-Shot Recording at 2.1 Tsample/s and 104 Mframes/s Using Temporal Imaging

We demonstrate temporal imaging with -42.6x time magnification of 200 ps frames with subpicosecond resolution for waveforms containing 2.5 Gb/s modulated picosecond pulses. 852 GHz signal bandwidth is captured single-shot at 104 MHz frame rates.

Compact fiber laser for 589 nm laser guide star generation

In this paper, we developed an all-fiber laser system for generating a 589 nm source for laser-guided adaptive optics. The design is based on sum-frequency mixing two fiber lasers in a nonlinear material to produce a CW output at the desired wavelength. Combining an Er/Yb:doped fiber laser operating at 1583 nm with a 938 nm Nd:silica fiber laser, one can generate 589 nm via sum-frequency mixing in a periodically poled crystal. The integrated system design and performance is presented

Compact fiber laser system for 589 nm laser guide star generation

Laser guided adaptive optics for astronomy can significantly improve the resolution of ground-based telescopes. We are developing an all-fiber 589nm laser system for this application by sum-frequency mixing 1583nm Er/Yb:doped and 938nm Nd:silica fiber lasers in a periodically poled crystal. Both CW and pulsed formats are under development.

High conversion efficiency solid-state 263-nm laser for triggering high-voltage switches at Sandia's Z-accelerator

Several advanced technologies, including phase conjugation with non-hazardous fluorinert and harmonic conversion with large 2 × 2 × 1 cm BBO crystals, were used to generate near diffraction-limited, 2.4-J, 20-ns-long pulses at 263-nm.